1. Field of the Invention
Embodiments of the invention relate to a stereoscopic image display capable of implementing a two-dimensional plane image (hereinafter referred to as “2D image”) and a three-dimensional stereoscopic image (hereinafter referred to as “3D image”).
2. Discussion of the Related Art
A stereoscopic image display implements 3D image using a stereoscopic technique or an autostereoscopic technique.
The stereoscopic technique, which uses a parallax image between left and right eyes of a user with a high stereoscopic effect, may include a glasses type method and a non-glasses type method. In the glasses type method, the parallax image between the left and right eyes is displayed on a direct-view display or a projector through a change in a polarization direction of the left and right parallax image or in a time-division manner, and thus a stereoscopic image is implemented using polarization glasses or liquid crystal shutter glasses. In the non-glasses type method, an optical part such as a parallax barrier and a lenticular lens for separating an optical axis of the left and right parallax image is generally installed in front of or behind a display screen, and thus the stereoscopic image is implemented.
FIG. 1 illustrates an example of a stereoscopic image display implemented as a liquid crystal display. As shown in FIG. 1, a glasses type stereoscopic image display implements a stereoscopic image using polarization characteristic of a patterned retarder 5 disposed on a display panel 3 and polarization characteristic of polarization glasses 6 a user wears. The display panel 3 assigns a left eye image L and a right eye image R to adjacent display lines and displays the left and right images L and R. The patterned retarder 5 varies polarization characteristics of the left eye image L and the right eye image R differently from each other and separates polarizations of the left eye image L and the right eye image R. A left eye filter of the polarization glasses 6 transmits the polarization of the left eye image L and intercepts the polarization of the right eye image R. A right eye filter of the polarization glasses 6 transmits the polarization of the right eye image R and intercepts the polarization of the left eye image L. In FIG. 1, a reference numeral 1 denotes a backlight unit providing light to the display panel 3, and reference numerals 2 and 4 denote polarizing films respectively attached to an upper substrate and a lower substrate of the display panel 3.
In the stereoscopic image display shown in FIG. 1, visibility of a 3D image is degraded due to a crosstalk generated at a position of a vertical viewing angle. A left eye of the user has to transmit only light of the left eye image L and a right eye of the user has to transmit only light of the right eye image R, so that the user sufficiently feels a stereoscopic feeling of the 3D image. However, there exists a period in which both light of the left eye image and light of the right eye image are incident on each of the left and right eyes of the user in the related art stereoscopic image display. This may lead to a left/right eye crosstalk in which the user sees both light of the left eye image and light of the right eye image through the user's left or right eye.
When the users does not watch the 3D image in the front of the display panel 3 and looks down or up the 3D image, each of a left eye patterned retarder 5a and a right eye patterned retarder 5b transmits both light of the left eye image and light of the right eye image at a vertical viewing angle greater than a front viewing angle by an angle equal to or greater than a predetermined angle. This may lead to the crosstalk. Thus, the related art stereoscopic image display has the very narrow vertical viewing angle at which the 3D image is displayed without generating the crosstalk.
Thus, as shown in FIG. 2, Japanese Laid Open Publication No. 2002-185983 discloses a method for widening a vertical viewing angle of a stereoscopic image display by forming black stripes BS on a patterned retarder 5. When the users observes the stereoscopic image display at a location spaced apart from a stereoscopic image display by a predetermined distance D, a vertical viewing angle α, at which the crosstalk is not theoretically generated, depends on the size of black matrixes BM of a display panel 3, the size of the black stripes BS of the patterned retarder 5, and a distance S between the display panel 3 and the patterned retarder 5. The vertical viewing angle α widens as the size of the black matrixes BM and the size of the black stripes BS increase and as the distance S between the display panel 3 and the patterned retarder 5 decreases. On the other hand, the stereoscopic image display disclosed in Japanese Laid Open Publication No. 2002-185983 interacts the black matrixes BM of the display panel 3, thereby generating Moire. Further, the stereoscopic image display disclosed in Japanese Laid Open Publication No. 2002-185983 displays the 2D image with greatly reduced luminance because of the black stripes BS of the patterned retarder 5.
As shown in FIG. 3, the present applicant has proposed a structure and a driving method of a panel for dividing each of red (R), green (G), and blue (B) subpixels PIX of a display panel into two division cells 10 and 20 and controlling one of the division cells 10 and 20 using an active black stripe in U.S. application Ser. No. 12/536,031 (Aug. 5, 2009) which are hereby incorporated by reference in their entirety. In other words, each of the subpixels PIX is divided into a main pixel part 10 and a subpixel part 20. The main pixel part 10 includes a thin film transistor (TFT) T1 positioned at a crossing between a data line D1 and an n-th gate line Gn and a first liquid crystal cell Clc1 connected to the TFT T1, where n is a natural number. The subpixel part 20 includes a TFT T2 positioned at a crossing between the data line D1 and an (n+1)-th gate line Gn+1 and a second liquid crystal cell Clc2 connected to the TFT T2. The subpixel part 20 operates as a pixel to which 2D image data is written in a 2D mode and may operate as an active black stripe to which black data is written in a 3D mode.
A stereoscopic image display disclosed in U.S. application Ser. No. 12/536,031 can solve the problems of the stereoscopic image display appearing in Japanese Laid Open Publication No. 2002-185983. The stereoscopic image display disclosed in U.S. application Ser. No. 12/536,031 may prevent a luminance reduction of a 2D image by dividing each of the subpixels PIX into two parts and writing the 2D image data to each of the divided pixels PIX in the 2D mode. Further, it may improve the visibility of both the 2D and 3D images by widening a vertical viewing angle in the 3D mode. Hence, it may achieve more excellent display quality than the existing stereoscopic image display.
A gate driving circuit includes a level shifter and a shift register. The shift register may be formed directly on a substrate of a display panel through a Gate In Panel (GIP) process. The level shifter is being developed for the exclusive use of the 2D mode. However, when outputs of the gate driving circuit in the 2D and 3D modes are different from each other, it is impossible to operate the gate driving circuit using only the existing level shifter for the exclusive use of the 2D mode.